Evan Ebel, the prime suspect in the shooting death of Colorado prison chief Tom Clements, was released from prison four years early because of a clerical error, court officials said today.

Ebel, 28, was released from a Colorado jail in January.

In 2008, he agreed to a plea deal after assaulting a prison guard at Fremont Correctional Facility. He was supposed to complete a sentence of up to four additional years in prison for that assault, to be served after he completed the eight-year sentence he had been serving since 2005.

"The judge announced a sentence of four years in the Department of Corrections but did not state it was consecutive because it was already required by the terms of the plea agreement," Walter Blair, the judicial district administrator for Colorado's 11th Judicial District, and Chief Judge Charles Barton said in a written statement.

"Because the judge did not expressly state that the sentence was consecutive, the court judicial assistant did not include that term in the [court order] that went to the Department of Corrections," the statement said.

When prisons officials believed that Ebel had finished his court-ordered sentence, they released him on Jan 28.

Ebel was on parole from Colorado prisons and was not legally allowed to purchase a weapon. He is believed to have used a gun to kill Clements on March 19 at Clements' Colorado home. He is also believed to be involved in the death of a Domino's delivery man, Nathan Leon, in Denver.

Ebel was then pulled over by Texas authorities two days later and engaged in a high-speed chase and gun battle with them. He was shot and died later at a hospital.

"The court regrets this oversight and extends condolences to the families of Mr. Nathan Leon and Mr. Tom Clements," said the statement signed by Blair and Barton.

Law enforcement sources told ABC News on March 28 that they were investigating whether Clements' death was orchestrated by members of Ebel's white supremacist prison gang, 211 Crew. They were still trying to determine whether others were involved in Clements' death.

In 2005, Ebel slipped out of his handcuffs while being transferred from a cell and punched a prison guard in the nose, The Associated Press reported.